Various apparatus have been described in the prior art for the generation of carbon dioxide snow. For example, in U.S. Pat. No. 3,757,367, the patentee discloses a J-shaped conduit through which liquid carbon dioxide is passed and in which the pressure on the liquid carbon dioxide is reduced so as to provide carbon dioxide snow entrained in a carbon dioxide vapor flow. The patent uses a circular flow path in order to separate the snow by centrifugal force from the vapor. An electrically warmed discharge port is provided along the curved portion of the J-tube so that the solid carbon dioxide in the form of snow is removed and downwardly discharged from the apparatus. This apparatus provides a narrow concentrated discharge pattern of carbon dioxide snow. A heating element is utilized or proposed because of problems with the clogging of the discharge port of this carbon dioxide snow generator.
In another example of the prior art, U.S. Pat. No. 3,807,187 discloses the utilization of a J-tube as well as a direct discharge snow horn for the production and delivery of carbon dioxide snow. This patent recognizes the problems inherent in apparatus for the production of carbon dioxide snow, namely the build-up of undesirable levels of carbon dioxide gas in the environment surrounding the snow generation operation. For the safety of operating personnel, such build-ups of carbon dioxide gas must be vented. The patent suggests the powered removal of carbon dioxide vapors. This teaching also discloses a small discharge outlet which redirects the carbon dioxide snow from a J-tube.
In U.S. Pat. No. 4,111,671 the patentee teaches the use of a rectangular cross-sectioned J-tube in which the cross-section is of increasing area as one leaves from the liquid input end of such tube. The cross-sectional change is made to reduce the pressure to allegedly provide greater separation of the solid and vapor phases.
U.S. Pat. No. 4,166,364, assigned to the same assignee as the present invention, discloses a carbon-dioxide snow hood which incorporates a J-tube and a diffuser chamber which chamber reverses the flow of carbon dioxide snow, while at the same time diffusing the stream of snow into a wide low velocity pattern. Again, this patent does not address the purging of residual materials within the snow generating apparatus.
The prior art fails to provide any means for automatic cleaning or purging of carbon dioxide snow generating apparatus. The clogging or deposition of dry or water ice on various operating surfaces of carbon dioxide snow generating apparatus is known to occur. Such clogging and deposition can provide operational as well as sanitary problems for such snow generation.
Therefore, it is an object of the present invention to provide means for the automatic purging of carbon dioxide snow from various surfaces of the snow generating apparatus.
It is also an object of the present invention to provide means for exhausting entrained water from the apparatus prior to snow generation and the potential formation of water ice.
It is another object of the present invention to provide snow generation apparatus in which the surfaces have a reduced tendency to retain carbon dioxide snow or water ice.
It is yet another object of the present invention to provide means for achieving the above objects in an automatic operation of purging apparatus included in the carbon dioxide snow generating apparatus of the present invention.